Question

In the movie, The Martian, an astronaut (played by Matt Damon) is stranded on Mars. When he sends a message to Earth in the form of radio or microwaves, he must then wait for a reply. Given that the closest approach Mars makes to Earth is 35.8 million miles (or 57.6 million km), what is the minimum elapsed time astronaut Matt would have to wait for a reply to his message? C=3.00 x 10^8 m/s radius of earth= 6400 km Circumference = 2pir

Answer 1

Giv n that the minimum distance between Mars and Earth is 57.6 million km.

Speed of light = 3*10^(8) m/sec = 3*10^(5) km/sec

So assuming that as soon as the signal reaches from Mars to Earth, the reply is sent back from Earth to Mars without any delay( to minimize the time duration ). This means that message must travel twice the distance ( Mars to Earth and back to Mars) with speed of light( as message is an electromagnetic wave).

So minimum time = 2*57.6*1000000/3*10^(5)

Time = 384 seconds.

So minimum time elapsed for reply is = 384 seconds Ans.